A15N NMR study ofin vivo cerebral glutamine synthesis in hyperammonemic rats
| Autor: | Brian D. Ross, Keiko Kanamori, Farhad Parivar |
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| Rok vydání: | 1993 |
| Předmět: |
Male
medicine.medical_specialty Magnetic Resonance Spectroscopy Glutamine Glutamic Acid Biology Sensitivity and Specificity chemistry.chemical_compound Glutamates Biosynthesis Ammonia Glutamate-Ammonia Ligase In vivo Glutamine synthetase Internal medicine medicine Animals Radiology Nuclear Medicine and imaging Rats Wistar Spectroscopy Dose-Response Relationship Drug Nitrogen Isotopes Portacaval Shunt Surgical Glutamate receptor Brain Hyperammonemia Glutamic acid medicine.disease Rats Quaternary Ammonium Compounds Disease Models Animal Dose–response relationship Endocrinology chemistry Hepatic Encephalopathy Molecular Medicine |
| Zdroj: | NMR in Biomedicine. 6:21-26 |
| ISSN: | 1099-1492 0952-3480 |
| DOI: | 10.1002/nbm.1940060104 |
| Popis: | Rats were given intravenous 15NH4+ infusion at a rate of 2.2 or 5.5 mmol/h/kg body wt to induce hyperammonemia, as animal models of hepatic encephalopathy. Its effect on cerebral amino acid metabolism was studied in vivo by 15N NMR spectroscopy at 20.27 MHz for 15N. Cerebral [gamma-15N]glutamine (present at a tissue concentration of 4-9 mumol/g) and [alpha-15N]glutamate/glutamine (6 mumol/g) were clearly observed in living rats within 9-18 min. In portacaval-shunted rats, final cerebral [gamma-15N]glutamine concentrations were higher than those in controls after the same infusion period, presumably because decreased 15NH4+ removal in the liver led to increased 15NH3 diffusion into the astrocytes. In control rats, cerebral [gamma-15N]glutamine pool increased at a rate of 1.7 mumol/h/g when blood ammonia concentration was 0.8 mM. 15N enrichment in gamma-15N was 71%. From these observations, in vivo activity of glutamine synthetase in rat brain was estimated to be 3.5 mumol/h/g. Comparison with reported optimum in vitro activity suggests that in situ concentrations of some substrates and cofactors limit the activity of glutamine synthetase in vivo. |
| Databáze: | OpenAIRE |
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